Method and apparatus for multiple readout of digital video data with faster playback mode switching

Abstract

A multiple readout of digital video data, capable of realizing the fast forward and fast reverse modes even under the logically multiplexed circumstances, and reducing a time required for the playback mode switching. A cycle for a readout operation is formed by a plurality of slots, each slot representing a unit time for reading a unit amount of the digital video data for each channel assigned to each user terminal; at least one of the plurality of slots forming each cycle is allocated to each channel and at least one of the plurality of slots not yet used for any channel in each cycle is additionally allocated to a user terminal which is requesting a playback mode switching; and the readout operation to read the digital video data for each channel from the storage device is carried out at every slot allocated to each channel in each cycle, by cyclically repeating the cycle for the readout operation. The requested playback mode switching can be a switching to a fast forward/reverse mode.

What is claimed is: 
     
       1. A method for multiple readout of digital video data stored in a storage device, in response to requests from a plurality of user terminals, comprising the steps of: forming a cycle for a readout operation by a plurality of slots, each slot representing a unit time for reading a unit amount of the digital video data for each channel assigned to each user terminal;   allocating at least one of said plurality of slots forming each cycle to each channel and additionally allocating at least one of said plurality of slots not yet used for any channel in each cycle to a user terminal which is requesting a playback mode switching; and   carrying out the readout operation to read the digital video data for each channel from the storage device at every slot allocated to each channel at the allocating step in each cycle, by cyclically repeating the cycle for the readout operation formed at the forming step.   
     
     
       2. The method of claim 1, wherein at the allocating step, the user terminal which is requesting the playback mode switching requests a switching to a fast forward/reverse mode. 
     
     
       3. The method of claim 2, wherein said at least one of said plurality of slots to be additionally allocated at the allocating step is at least one spare slot reserved for the fast forward/reverse mode provided in each cycle in advance. 
     
     
       4. The method of claim 2, further comprising the step of continually allocating at least one of said plurality of slots not used for any channel in each cycle to the user terminal which requested the playback mode switching and subsequently continues to request the fast forward/reverse mode after the playback mode switching. 
     
     
       5. The method of claim 1, wherein said at least one of said plurality of slots to be additionally allocated at the allocating step is at least one vacant slot not yet allocated to any channel in each cycle. 
     
     
       6. The method of claim 1, wherein said at least one of said plurality of slots to be additionally allocated at the allocating step is at least one vacant slot allocated in advance to some channel but not used in the readout operation for said some channel. 
     
     
       7. The method of claim 1, further comprising the steps of: transferring the digital video data for each channel read out at the reading step to each user terminal assigned with each channel; and   decoding and displaying the digital video data transferred at the transferring step on each user terminal.   
     
     
       8. An apparatus for multiple readout of digital video data stored in a storage device, in response to requests from a plurality of user terminals, comprising: means for forming a cycle for a readout operation by a plurality of slots, each slot representing a unit time for reading a unit amount of the digital video data for each channel assigned to each user terminal;   means for allocating at least one of said plurality of slots forming each cycle to each channel and additionally allocating at least one of said plurality of slots not yet used for any channel in each cycle to a user terminal which is requesting a playback mode switching; and   means for carrying out the readout operation to read the digital video data for each channel from the storage device at every slot allocated to each channel by the allocating means in each cycle, by cyclically repeating the cycle for the readout operation formed by the forming means.   
     
     
       9. The apparatus of claim 8, wherein the user terminal which is requesting the playback mode switching requests a switching to a fast forward/reverse mode. 
     
     
       10. The apparatus of claim 9, wherein said at least one of said plurality of slots to be additionally allocated by the allocating means is at least one spare slot reserved for the fast forward/reverse mode provided in each cycle in advance. 
     
     
       11. The apparatus of claim 9, further comprising means for continually allocating at least one of said plurality of slots not used for any channel in each cycle to the user terminal which requested the playback mode switching and subsequently continues to request the fast forward/reverse mode after the playback mode switching. 
     
     
       12. The Apparatus of claim 8, wherein said at least one of said plurality of slots to be additionally allocated by the allocating means is at least one vacant slot not yet allocated to any channel in each cycle. 
     
     
       13. The apparatus of claim 8, wherein said at least one of said plurality of slots to be additionally allocated by the allocating means is at least one vacant slot allocated in advance to some channel but not used in the readout operation for said some channel. 
     
     
       14. The apparatus of claim 8, further comprising means for transferring the digital video for each channel read out by the carrying out means to each user terminal assigned with each channel, wherein each user terminal decodes and displays the digital video data transferred thereto by the transferring means.